Combined damages from Hurricanes Harvey and Irma could cost the U.S. economy as much as $290 billion, according to a new forecast.

Hurricane Harvey, which battered Houston with record amounts of torrential rain and flooding last month, is estimated to be one of the costliest weather disasters in U.S. history and Irma is expected to cause record-breaking damages as well, AccuWeather President Joel Myers said in a statement Sunday.

"We believe the damage estimate from Irma to be about $100 billion, among the costliest hurricanes of all time. This amounts to 0.5 of a percentage point of the GDP of $19 trillion," Myers said. "We estimated that Hurricane Harvey is to be the costliest weather disaster in U.S. history at $190 billion or one full percentage point of the GDP."

"Together, AccuWeather predicts these two disasters amount to 1.5 of a percentage point of the GDP, which will about equal and therefore counter the natural growth of the economy for the period of mid-August through the end of the fourth quarter," he added.

"Some of the losses will be covered by insurance, some will not, so the losses will be felt in a variety of ways by millions of people," Myers said. "Many millions of people have already been evacuated, so their lives have already been affected and they have incurred costs of one sort or another."

At least five people died of storm-related injuries in Florida, including a sheriff's deputy, as Irma barreled across the Sunshine State with punishing wind gusts of up to 142 mph at its height. At least 27 people died in the Caribbean.

More than 4 million people were without power in Florida on Monday and many towns and cities imposed curfews. Miami-Dade police said early Monday they arrested 28 people for burglary and looting. Fort Lauderdale police also said they arrested several looters. More than 73,000 were powerless in Georgia.

Irma made landfall in the Florida Keys on Sunday morning bringing powerful winds, rain and flooding. The storm swamped parts of Naples and Miami on opposite coasts before moving north over the center of the state.

The National Hurricane Center (NHC) said it expected the storm’s center to remain inland over Florida and then move into Georgia, Alabama and Tennessee where heavy rain and possible flash floods will be a major concern.

"This is a story for many days to come, and Florida will be ravaged the most through Sunday night and maybe north Florida Monday morning," Myers said.